It's probably too much to hope for for VBA to run games full speed.
I'll tell you why. Unless there have been huge speed gains in VBA in the past 2 years, the PSP probably can't handle it. My last computer was a Celeron-433 and it couldn't run VBA without substantial frameskipping involved.
If a 433 mhz computer with 10 times the RAM of a PSP can't handle fullspeed GBA emulation, the PSP probably can't either.
There's room for improvement on the present version, certainly, but unless the porter wants to recode substantial portions in PSP-assembler, we're probably not going to see full speed.